The present invention relates to respiratory masks, especially such masks for breath-by-breath ventilation measurements with respect to humans, in conjunction with a perimeter gel seal for the mask.
Medical clinicians, physical therapeutist and the like often very closely analyze the gas content of the exhaled breath of a person being medically tested or placed under some type of physical activity. Technology has developed in this field to a point where it is possible to analyze the gaseous percentage of exhaled breath of the person being tested and to quite closely analyze the various amount of the gasses components that are contained within each breath. In the past when such tests were first run, the analytical techniques were unable to provide extremely accurate analysis of the gasses. Consequently, general trends were studied more than specific analysis of each breath. With the improvements in the analytical techniques this has changed so that each breath can be carefully studied and the analytical techniques are sufficient to provide a very accurate analysis of the gasses components of each breath.
Because the analytical techniques have improved, the major problems associated with highly accurate analyses have switched from problems in chemical analysis to preventing the presence of dead spaces and/or leaks within the testing equipment. Consequently, there have been recent attempts in this industry to try to develop masks which highly conform to the face of the user and create comparatively very little dead space within the mask itself so there is little gas that collects between the user and the analytical equipment. A mask of the type that has been designed to limit dead space is shown in U.S. Pat. No. 5,265,595 to Kevin Rudolph who is one of the co-inventors of the present application and which is incorporated herein by reference.
While limitation of the dead space within the mask has made analytical measurements more accurate, a small leakage sometimes occurs around the periphery of the mask where it sits upon the face of the user, thereby allowing escape of gasses from the mask or outside air into the mask, such that the analysis of the exhaled gases is less accurate then it would be if no such leakage occurred.
One of the major problems with masks of this type is that the mask is made for a "standard face". As can be readily determined by viewing a number of persons, face contours and overall shape of people vary substantially as well as does the relative size of the persons' head and consequently their face. Because of these variations it is not possible to make a mask that will fit every single person exactly. Even if a mask could be made to fit a person exactly, movement of various muscles in the face, such as during physical activity or breathing, may slightly disrupt the seal of the mask.
Consequently, applicants have attempted to find a suitable material which will provide a good seal between the mask and the face of a user, while allowing the mask and seal to be easily removed after usage and further such that the seal does not cause any substantial harm or injury to the user. The inventors were unable to find any type of such sealing material which was suitable for the purpose and which was currently used in conjunction with masks. Therefore, they set about finding and developing a material which would be suitable for this purpose.